Convertible seat bed units of various constructions and useable both for seating and sleeping are well known in the art. In many of these, a flexible bed platform is held in a curved condition in a sofa portion of the seat bed unit. Once the seat cushions are removed, the bed platform can be slid out of the sofa portion and is straightened out. Convertible sofa-bed units are also known in which a rigid seat support frame is mounted on a main frame for movement of the seat between a rearward seating position--in which a rear edge of the seat is located under a back rest--and a forward sleeping position, in which the rear edge of the seat is located forwardly of the backrest and is raised to level the bed. A typical patent disclosing such an embodiment is the Quakenbush U.S. Pat. No. 3,816,860. Another such sofa-bed unit is disclosed in the Fox U.S. Pat. No. 3,005,997.
In the known art as exemplified by these two patents, the angle at which the seat frame is oriented in relation to a horizontal plane parallel to the floor changes as the seat frame is moved from its seating position to its sleeping position. In the seating position, the seat frame is disposed at an acute angle to a horizontal plane. In the sleeping position, the seat frame is disposed in the horizontal plane. The angle of the seat frame changes because it is desirable, when the seat frame is used for sleeping, to have the seat frame be parallel to the floor surface, and hence the horizontal plane, so that a person sleeping on the seat frame of the sofa-bed does not roll off the seat frame or roll into the backrest of the sofa. In contrast, in a normal seated position, it is desirable to position the seat frame at an acute angle to the horizontal so that a seated person does not slide off the sofa. To this end, the seat frame is normally tilted in relation to a horizontal plane by approximately 1.degree. to 3.degree. or so.
One of the problems with conventional couches and seats is that for a person with long legs, the seat portion of the couch or chair is usually not long enough to support all of the thigh of the person so that the backs of the knees are supported by the seat cushions. If the known sofa-bed units disclosed in the Quakenbush '860 patent and the Fox '997 patents were to have their seat frames moved forward, this would accommodate the legs of longer persons. However, the orientation of the seat frames would be changed from an acute angle to the horizontal--which is desirable when sitting--to the horizontal plane. This orientation is uncomfortable for seated persons as they would have a tendency to slide off the seat frame.
Another problem with conventional couches and seats is that the extension of the seat frame in relation to the main frame cannot be controlled so that the seat frame can be locked in relation to the main frame at a number of positions between a fully retracted position and a fully extended position. Rather, in the sofa-bed units disclosed in the Quakenbush '860 patent and the Fox '997 patent, there is only a fully retracted position and a fully extended position. This is understandable since the thrust of both of these patents is to a sofa which converts into a bed rather than a sofa having a slidable seat section.
In addition, the known sofa-bed units do not allow a sliding motion of the seat frame in relation to the main frame when a person is seated on the seat frame. Rather, the person has to get up to move the seat frame. This is understandable because the seat frame is being turned into a bed.
It would be desirable to have the seat frame which, when slid forwardly, maintains an acute angle in relation to the main frame so that a person sitting on the seat frame can have the backs of his knees supported by the seat cushions while at the same time not having a tendency to slide off the seat cushions because of a change in the orientation of the seat frame in relation to the horizontal plane. It would also be desirable to have a seat frame that can be moved while the person remains seated and that can be locked into a number of positions between a fully retracted position and a fully extended position so that the person can regulate the length of the seat portion.
Accordingly, it has been considered desirable to develop a new and improved seating system which can be used on couches, love seats or chairs which would overcome the foregoing difficulties and others, meet the above stated needs and provide better and more advantageous overall results.